Alternative methods to revive a fully discharged Vanmoof S3 Main battery
TLDR, I revived my fully discharged & non-responsive S3 battery without a bench charger/NiMH charger/taking out the main battery from the frame.
Full story,
My S3 has been sitting idle for 5 months, and the battery is completely dead. The screen is non-responsive after pressing the reset button. No sound either. I went through the community posts for solutions. The usual solutions involve a variable DC bench charger or NiMH battery charger, none of which I have. The battery refused to charge when plugged in due to ultra-low voltage. Also, I don't have enough eletricity-related knowledge to carry out a 'surgery' on the batteries due to safety concerns.
Right before I recycled the bike, credit is where the credit is due, my partner stumbled upon a Chinese tiktok video about how to repair the more-common electric mopeds with depleted batteries. Thank you, the Chinese stranger, you saved me a couple hundred pounds.
This method doesn't require extensive electricical knowledge, and it shall impose relatively lower level of risk. I personally haven't seen this method mentioned before, so I would like to share here for anyone not-so-handy like me.
Still, it's electric, it's scary. DISCLAIMER, carry at your own risk.
The solution is as followed,
flip the bike upside down.
plug in the charger (the charger shows green light, since it refused to charge)
spin the FRONT wheel backwards like crazy. (with elbow grease/rotary tool/anything you like)
keep spinning for around 15-30min
magically, the charger turns red, and the bike will start taking the charge.
leave it charging till full like usual...annnd that's it.
I am shocked by the fact this even worked. I assume the backwards-spinning wheel sent trickles of power pulses to trick the smart module to start charging.
I cannot guarantee this solution is as universal as the other methods.
I also need point out there are two things that might make the case different.
Since the bike is completely dead, and the bike is not responsive whatsoever. I chose to extract the small battery in the upper frame smart module. I used a 'TP4056' USB-C module to briefly charge it.
The charging brick I have is not the official vanmoof charger since it was stolen. Mine is a aftermarket 42V-3A charger that aims at vanmoof users. This supposedly runs at slightly lower voltage than the official charger. I am unsure if this makes a difference.
Not a good writer, might be too long.
Hope this would be helpful for someone in the future.